A fan generally utilizes rotating blades to generate airflow so as to dissipate the heat from electronic devices. When the fan rotates, the balance of rotating fan is basically required. A conventional fan, which is disclosed in U.S. Pat. No. 6,648,602 entitled “fan having balancing blade sets”, comprises a central hub, a shaft and at least three blade sets. The shaft is formed through and axially extends from the central hub. The blade sets are formed radially and outward extending from a ring-wall of the central hub in stagger arrangement, and properly have different included angles for stable rotation of the fan. However, the three blade sets must have equivalent total mass (weight) to enable the three blade sets to be balanced in regard to the shaft during rotating. The fan will shake and unbalance to affect the airflow while the fan rotates if there is no equivalent total mass among the three blade sets. The conventional fan without equivalent total mass of the three blade sets cannot be reworked and has to be abandoned because that the three blade sets are formed together by plastic injection.